Method and apparatus for impregnating fibrous filter material

ABSTRACT

THE FILTER MATERIAL IS DEPOSITED ONTO THE ROTATING DELIVERY ROLLER PRIOR TO ENTRY OF THE TRAVELLING WEB OF TOW BETWEEN THE NIP OF THE DRIVEN ROLLER AND IDLER ROLLER SO THAT THE FILTER MATERIAL IS FORCED INTO THE WEB UPON PASSING THROUGH THE NIP. THE EMBEDDING OF THE FILTER MATERIAL INTO THE ERB IN THE NIP SERVES TO DISTRIBUTE THE MATERIAL MORE UNIFORMLY THROUGH THE CROSS-SECTION OF THE TWO BEFORE THE TWO IS GATHERED TOGETHER AND FORMED INTO A ROD.

y 3, 1973 A. CALLESON METHOD AND APPARATUS FOR IMPREGNATING FIBROUSFILTER MATERIAL Filed Jilly a, 1971 INVENTOR. Dov/1w A. a ua-say jrr-never;

United States Patent 3,743,528 METHOD AND APPARATUS FOR IMPREGNATINGFIBROUS FILTER MATERIAL Donald A. Calleson, Durham, N.C., assignor toLiggett & Myers Incorporated, New York, N.Y. Filed July 8, 1971, Ser.No. 160,834 Int. Cl. B44c N08 US. Cl. 1179 16 Claims ABSTRACT OF THEDISCLOSURE The filter material is deposited onto the rotating deliveryroller prior to entry of the travelling web of tow between the nip ofthe driven roller and idler roller so that the filter material is forcedinto the web upon passing through the nip. The embedding of the filtermaterial into the web in the nip serves to distribute the material moreuniformly through the cross-section of the tow before the tow isgathered together and formed into a rod.

This invention relates to an apparatus and method for impregnating a webof fibrous filter material. More particularly, this invention relates toan apparatus and method for impregnating granulated filter material intoa travelling web of fibrous filter material.

Heretofore, it has been known to impregnate travelling webs of fibrousfilter materials such as tow with various fluids and solids in order toimprove the filtering qualities of the tow when subsequently formed intoa rod for cigarette filters and applied to cigarettes. In some cases,the travelling length of tow has been coated with resin while, in othercases, charges of granulated material have been deposited on the towprior to the formation of the web of tow into a rod. For example, it hasbeen known to deposit spaced apart charges of granulated material ontothe top surface of a travelling web of tow and to thereafter gather theweb into a rod. However, the granulated materials which have beenincorporated into the tow in this manner have not been uniformlydispersed throughout the tow such that the subsequently formed rodsections have varying concentrations of the granulated materialthroughout. Also, in those instances where the granulated material hasbeen applied as a uniform layer on a travelling web of tow, thesubsequent gathering and forming of the web into a rod causes the layerof granulated material to be concentrated either in the form of a corecylinder in the rod or in the form of a layer with a woundcross-section. Because of thesevariances in the distribution of thegranulated materials in the formed rods, the filters made from the rodshave had sections in which only the fibrous filter material is availableto filter the smoke and gases generated during smoking of a cigarette.As a result, the efiiciency of the filter has been reduced.

Accordingly, it is an object of this invention to provide an improvedimpregnated filter for cigarettes.

It is another object the invention to uniformly disperse an adsorptiontype filter material throughout a fibrous filter plug.

It is another object of the invention to provide an apparatus forintroducing filter material into a travelling web of fibrous filtermaterial for uniform dispersal throughout the travelling web.

Briefly, the invention provides a method of imp-regnating a travellingweb of fibrous filter material in which a layer of granular filtermaterial is placed in adjacent relation to at least one side of thetravelling web and both the web and granular layer are passed through arestricted passageway in which the granular filter material is forcedinto and dispersed throughout the crosssection of the web. In order tohave the granular particles embedded into the web during travel throughthe restricted passageway, the combined thickness of the filter materialand web is of a greater dimension than the height of the restrictedpassage. After passage through the restricted passage, the impregnatedweb is gathered together and formed into a rod which is subsequentlysevered into a series of impregnated fibrous filter material plugs. Asthe layering of the granular material on the web is carried out in auniform and continuous fashion, the subsequently formed rod has auniform dispersal of filter material throughout the length thereof.

The apparatus of the invention includes a means for driving a web offibrous filter material, such as tow through a restricted passageway andmeans for placing the layer of granular filter material in adjacentrelation to at least one side of the web upstream of the restrictedpassageway so that the granular material and the web can be directedthrough the restricted passageway simultaneously. In addition, theapparatus includes a' means for adjusting the height of the restrictedpassageway to the size of the granular filter material particles and webso that the individual particles will be embedded into the web uponpassing through the restricted passageway.

In one embodiment, a pair of rotatable rolls are used to drive the weband to form a nip which serves as the restricted passage. The nip issized so that particles of granular filter material will be embedded inthe web during passage through the nip. In this embodiment, the granularfilter material is deposited onto the surface of the lower of the tworollers while the travelling web is delivered onto the surface of theroller at a point slightly downstream from the point in which thegranular filter material is deposited. In this way, the filter materialis disposed on the underside of the web prior to passage of the web andgranular filter material through the nip formed between the two rollers.As the granular filter material and web pass through the nip formed bythe two rollers, the filter particles are forced into the web by apressing action of the rollers and become dispersed throughout thecross-section of the web.

In order to feed the granular filter material to the travelling Web in auniform manner, the apparatus includes a suitable means, for example, avibratory feed, in which a supply of filter material is fed from ahopper onto a reciprocating or vibrating tray and from the tray onto aslide which delivers the material directly onto the roller. The slide isinclined in a downward direction and is flared in width at the end so asto uniformly distribute the filter material across the width of theroller, for example, the width of the slide is substantially the widthof the web of fibrous filter material.

The filter material which is used can be of any suitable particle size.In addition, where the particle size of the filter. material is of asize larger than the restricted passageway or nip, these largerparticles are crushed in passing through the restricted passageway ornip. This crushing serves to reduce the particles to a smaller particlesize.

After passing through the nip of the rollers the impregnated web issubsequently delivered to a rod forming means in which the impregnatedweb is formed into a rod. This rod is subsequently severed into suitablelengths of impregnated filter plugs. During gathering of the web intothe rod, the granular filter material is maintained in the uniformdispersed state so that the subsequently formed rod and plugs have auniform dispersal of the granular filter material through thecross-section and throughout the length of the rods and plugs.

These and other objects and advantages of the invention will become moreapparent from the following detailed description and appended claimstaken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a side view of an apparatus according to theinvention;

FIG. 2 illustrates an enlarged view of a pair of rollers used to formthe nip in which the filter material particles are forced into atravelling web; and

FIG. 3 illustrates a view of the feed apparatus for the filtermaterials.

Referring to the figures, the apparatus includes a supply bale for a web11 of fibrous filter material, for example of cellulose acetate tow anda drive means such as feed rolls (not shown) for pulling the Web 11 fromthe supply roll 10. In addition, an upper driven roller 13 and an idlerroller 14 form a nip through which the Web 11 is pulled through aplasticizer applicator (not shown) as is known and delivered to a rodforming section 17. Pressure is maintained between the rollers 13, 14 bythe weight of the upper roller 13 on the idler roller 14. A roller 15 isspaced below the roller 14 to define a nip 16 of predetermined size. Inaddition, a rod forming section 17 in which the web is gathered togetheras is known and formed into a rod 18 is located downstream of therollers 13, 14, 15 while a suitable severing means 19 is positioned atthe end of the rod forming section 17 to sever the rod 18 into a seriesof filter plugs 20.

The rollers 13, 14 are each pivotally mounted to pivot separately aboutthe same pivot shaft 21 so as to facilitate threading of the apparatus10 and to permit roller 14 to be adjusted with relation to roller 15 soas to control the nip 16 therebetween. The movement of the roller 14automatically moves the roller 13 as the roller 13 rests on the roller14. The roller 15 is mounted on a fixed axis and is chain driven by aseparate chain (not shown) from a chain (not shown) which drives roll13. The ratio of the diameters of rollers 13, 15 are equal to the ratioof the diameters of their respective drive sprockets to insure equalsurface speeds of the three rollers 13, 14, 15. Further, the shafts 22,23 of the rollers 13, 14 are each mounted on suitable box frames 24, 25to assure that all rolls are mounted parallel to each other. The frames24, 25 are, in turn, pivotally mounted on the pivot shaft 21.

In order to vary the size of the nip 16, the roller 14 is pivotedrelative to the roller 15 and secured in place in a suitable manner uponachieving the required spacing. For example, a suitable screw adjustmentcan be used to allow precise setting of the pivot angle of the roller14.

The apparatus further includes a means 26 for feeding granular filtermaterial 27 such as a granulated material, e.g. charcoal, or a materialsuch as diatomaceous earth to the roller 15 upstream of the nip 16 andupstream of the point where the web 11 contacts the roller 15. In thisway, the filter material 27 is disposed on the side of the travellingWeb 11 facing the roller 15. This feeding means 26 is in the form of avibratory feed system, as is known, which includes a hopper 28 for supplying material such as charcoal, diatomaceous earth, or any othersuitable filter material, a tray 29 which is mounted in a vibratorymanner below the hopper 28 to receive the filter material 27 and which,in turn, communicates with a depending slide 30 which is directedtowards the lower roller 15. The slide 30 increases in width from thetray 29 so that the material 27 which slides down the slide 30 isdispersed in a substantially uniform manner across the width of theroller 15. For example, the width of the slide 30 at the lower end issubstantially the width of the web 11 of tow supplied from the supplybale 10.

In addition, a chute 34 is located between the roller 15 and rod formingsection 17 to enclose the web 11 and layer of filter material 27 so asto contain any of the filter material which may fall off the web 11. Inthis way, any loose material is also delivered to the rod formingsection along with the web 11.

In operation, with the nip 16 adjusted relative to the thickness of theweb 11 and the layer of filter material 27, a continuous uniform layerof granulated filter material 27 is delivered from the feed means 26down the slide 30 onto the top surface of the roller 15 at a pointupstream of the nip 16 while a continuously travelling web 11 of tow isdrawn 011 the supply bale 10 and delivered into the nip 1'6. As the web10 and layer of granular material 27 travel through the nip 16 (FIG.2.), the particles 31 of the granular material which are of larger sizethan the nip 16 are crushed under the action of the two rollers 14, 15and disintegrate into smaller pieces 32. At the same time, all thegranular particles are pressed into the fibrous web 11 so as topenetrate into and embed in the web 10. Because of the crushing andpressing action of the rollers 14, 15 the particles of granular materialare dispersed throughout the crosssection of the web 10 in asubstantially uniform manner. Continued movement of the impregnated web11 into the gathering and rod forming section 17 produces a rod 18 ofimpregnated material in which the granular particles are uniformlydispersed throughout the cross section of the rod 18 and throughout thelength of the rod 18. Thereafter, the rod 18 is severed into theindividual plugs 20 and deposited into a hopper 33 or other suitablestorage means for subsequent usage.

It is noted that the initial clearance between the rollers 14, 15 can beset at a zero clearance without the tow web 11. This clearance willincrease to about 0.3 millimeter during passage of the web 11 throughthe nip 16, varying, of course, with the type of tow web 11 used. Thus,filter particles greater than 0.3 millimeter in diameter wouldexperience crushing such as in the case where granular carbon whichfalls within a particle size range of from 0.4 to 1.4 millimeters indiameter is used. The resulting reduction in average carbon particlesize has an effect of increased filtration efiiciency. In the case wherevery fine filter material particles are used, such as diatomaceous earthof a size of 0.15 millimeter or smaller, the pressing action of therollers 14, 15 embeds the filter material into the web 11 without anysignificant crushing of the filter particles.

The invention thus provides a technique of forcing granular filtermaterial into a tow web before the tow web is gathered to hold theparticles captive within the fiber matrix and keep to a minimum anyredistribution during rod forming. As a result, a greater percentage ofadditive can be embedded in the tow web and with greater uniformity.Also, a more efficient filter for a cigarette is obtained.

It is also noted that the web 11 of fibrous filter material which is ofgreater thicknes than the initial height clearance of the nip 16 is of aresilient nature such that the web 11 compresses in passing through thenip 16 to permit embedding or crushing of the solid substantiallynon-compressible granular particles under the forces of the rollers 14,15. The subsequent passage of the web 11 out of the nip 16 allows thefibrous filter material of the web 11 to expand to a free conditionwhile at the same time the granular material is enmeshed within thefibers of the web 11.

The invention further provides an apparatus which can be easilyincorporated into existing machinery in which travelling webs of tow aregathered together into rods.

The apparatus of the invention is further constructed of simplecomponents which are easily used and which are of a relatively low cost.As a result, improved filter plugs can be produced with relatively smallincreases in the cost of the equipment used to produce such plugs.

It is finally noted that any additive material placed on the surface ofthe roller 15 at the nip 16 between the rollers 14, 15 which is notembedded into the tow matrix web 11 will tend to be carried along on theupper surface of the web 11 and subsequently formed into the rod 18.

What is claimed is:

1. A method of impregnating a fibrous filter material web ofpredetermined thickness comprising the steps of conveying a length ofthe web through a path having a predetermined restricted passageway of aheight less than said thickness of the web therein;

placing a layer of granular filter material in adjacent relation to atleast one side of said web upstream of said restricted passageway, saidlayer of filter material and said web defining a thickness larger thanthe height of said passageway;

moving said web and said layer of filter material through saidpassageway simultaneously to embed the particles of said filter materialtherein and to disperse the particles through the cross-section of saidweb; and

thereafter gathering said web with said particles of material thereininto an axially elongated rod.

2. A method as set forth in claim 1 wherein said layer of particulatefilter material is placed substantially uniformly adjacent one side ofsaid web prior to movement through said restricted passageway.

3. A method as set forth in claim 2 wherein said web is moved throughsaid passageway at an angle from a vertical plane and said layer ofparticulate filter material is placed on the underside of said web.

4. A method as set forth in claim 1 wherein said layer of particulatefilter material is placed substantially uniformly and continuouslyadjacent said web.

5. A method as set forth in claim 1 wherein said restricted passagewayis formed by a pair of rotating rollers.

6. A method as set forth in claim 1 wherein said restricted passage isadjustable in height to accommodate different sizes of particulatematerial and to vary the degree of embedding of said particles.

7. A method as set forth in claim 1 which further comprises thesubsequent step of severing the rod into a series of impregnated filterelements.

8. A method as set forth in claim 1 wherein said filter material isgranular and includes particles of sizes larger than the height of saidpassageway and wherein said larger sized particles are crushed in movingthrough said restricted passageway.

9. A method of impregnating a travelling web of fibrous filter materialcomprising the steps of conveying the web through a predetermined path;placing a layer of granular filter material in adjacent relation to atleast one side of said web within said path; moving said web and saidlayer simultaneously in said path while compressing said web andpressing said layer into said web to crush and disperse the particles ofsaid layer through the cross-section of said web; and thereaftergathering said web with said particles of material therein into anaxially elongated rod with said particles uniformly distributed therein.10. An apparatus for impregnating a web of fibrous filter materialcomprising a pair of rotatable rollers for driving a length of the Web;a third rotatable roller forming a nip with one of said pair of rollersdownstream of said pair of rollers; means for placing a layer ofgranular filter material in adjacent relation to at least one side ofsaid web upstream of said nip for passage through said nipsimultaneously with said web; and

means for adjusting the height of said nip to cause embedding of theparticles of said layer during passage through said nip for dispersalthrough the cross-section of said web.

11. An apparatus as set forth in claim 10 wherein said one roller isadjustably mounted with respect to said third roller to vary the heightof said nip.

12. An apparatus as set forth in claim 10 wherein the filter material isgranulated and said rollers forming said nip are disposed to causecrushing of the granulated filter material therebetween during embedmentinto the web.

13. An apparatus as set forth in claim 10 wherein said means for placinga layer of particulate filter material includes a distribution means fordistributing said particles of said layer substantially uniformly acrossthe width of said web.

14. An apparatus as set forth in claim 13 wherein said distributionmeans includes a hopper for supplying said filter material, a vibratingtray below said hopper for receiving and displacing the supplied filtermaterial into a layer, and a slide extending from said tray to receivethe layer of filter material from said tray and to disperse said layeracross the width of said web.

15. An apparatus as set forth in claim 14 wherein said third roller ispositioned under said slide to receive the distributed layer of filtermaterial therefrom and to subsequently receive said web thereon oversaid distributed layer of filter material.

16. A method of making a filter for a cigarette comprising the steps ofconveying a length of a fibrous filter material web through a pathhaving a predetermined restricted passageway therein;

placing a layer of granular filter material in adjacent relation to atleast one side of said webupstream of said restricted passageway, saidlayer of filter material and said web defining a thickness larger thanthe height of said passageway; and

moving said web and said layer of filter material through saidpassageway simultaneously to crush the particles of said filter materialtherein and to disperse the crushed particles through the cross-sectionof said web.

References Cited UNITED STATES PATENTS 2,321,396 6/1943 Koch 117-9 X3,103,860 9/1963 Piquette 117-16 X 2,987,104 6/1961 Benedict 117-9 X2,936,814 5/ 1960 Yakubik 117-9 UX 2,354,113 7/1944 Gould 117-9 UX936,389 10/ 1909 Wadsworth 117-9 2,709,213 5/1952 Gibson 117-162,774,680 12/1956 Hackney et al. 117-17 3,013,891 12/1961 Block 117-17 X2,039,298 5/ 1936 Davidson 93-1 C X OTHER REFERENCES Defensive Pub.,Patent Ofiice, No. T880,009, November 1970, Harris, Apparatus andProcess for Obtaining Uniform Deposition of Finely Divided Additives onthe Surface of a Banded Cigarette Filter Tow.

WILLIAM D. MARTIN, Primary Examiner S. P. B'ECK, Assistant Examiner US.Cl. X.R.

